Aerodynamics Quiz 6

Consider the formation of oblique shockwaves. Across the oblique shockwave, the component of the flow velocity that is tangent to the wave:

• is constant

• increases

• decreases

• stagnates

For supersonic airfoils, the optimum angle of attack can be written as a function of the N/D ratio. The optimum angle of attack (in radian) is equal to:

• one-half times the reciprocal of the maximum N/D ratio

• one-half times the maximum N/D ratio

• reciprocal of the maximum N/D ratio

• two times the maximum N/D ratio

Increasing the value of the Mach number will cause the Mach angle to

• decrease

• increase

• remain constant

• reach zero degree

Whenever a supersonic flow is turned away from itself, an increase in the flow velocity will occur. The surface corner is

• convex

• concave

• upright

• horizontal

For the symmetrical double wedge airfoil, the value of the semi-vertex angle in radian is approximately equal to the:

• thickness-to-chord ratio

• angle of attack

• ratio of the cross-sectional area of the airfoil to the square of the chord

• Reynolds number

The main reason why supersonic airflows are designed to have sharp leading edges is to:

• prevent the formation of a detached bow shock in the leading edge

• encourage the flow of turbulent air near the leading edge

• to reduce interference drag

• to eliminate attached oblique shocks

Considering the diagram below for expansion waves, it is the angle that the rearward Mach line makes with respect to the upstream flow direction.

• µ2-θ

• µ2

• µ1

• µ1-θ

Considering oblique shockwaves, which of the following parameters will increase as the flow passes through the wave?

• Static Pressure

• Stagnation Temperature

• Component of the Mach Number tangent to the wave

• Mach Number

For a symmetrical airfoil, at zero angle of attack:

• no lift is generated

• lift is greater than drag

• lift is equal to weight

• parasite drag is zero

Let θ be the local angle of attack in radians Between the surface and freestream Mach number. For the expansive case where the freestream flow is turned away from itself, θ is treated as:

• negative

• positive

• zero

• One